[master] suppressed selfAssignment check for some rdata_txt_like test.

directly pushing.

src/cppcheck-suppress.lst

@@ -8,3 +8,4 @@ unreadVariable:src/lib/dns/rdata/template.cc:61
 selfAssignment:src/lib/dns/tests/name_unittest.cc:293
 selfAssignment:src/lib/dns/tests/rdata_unittest.cc:228
 selfAssignment:src/lib/dns/tests/tsigkey_unittest.cc:137
+selfAssignment:src/lib/dns/tests/rdata_txt_like_unittest.cc:222